Various polymers are widely used as crucial industrial materials in a variety of applications such as various industrial materials, textile materials, and construction materials. For example, aromatic polymers containing heteroatoms such as sulfur, oxygen, and nitrogen, including aromatic polythioethers such as polyarylene sulfide (PAS); aromatic polysulfones such as polysulfone (PSU), polyphenylsulfone (PPSU), and polyethersulfone (PES); aromatic polyetherketones such as polyetheretherketone (PEEK) and polyetherketone (PEK); aromatic polyethernitrile (PEN); and thermoplastic polyimides such as polyetherimide (PEI) are engineering plastics exhibiting excellent heat resistance, chemical resistance, flame retardancy, mechanical strength, electrical characteristics, dimensional stability, and the like. Because these materials can be molded into various molded products, films, sheets, fibers, and the like by general melt processes such as extrusion molding, injection molding, and compression molding, they are widely used in a wide range of technical fields such as electric devices, electronic devices, automobile instruments, and packaging materials.
Examples of production methods for such polymers include methods using a batch technique, and methods using a continuous technique have also been proposed. For example, Patent Documents 1 to 3 disclose continuous polymerization apparatuses for a polymer in which pressure-resistant polymerization vessels are connected in series, and a reaction solution is transported between the polymerization vessels by a pressure difference, and a continuous production method using the apparatus.